1. Field of the Invention
This invention relates to a plate cylinder of a printing press, wherein the plate cylinder includes a printing plate clamped onto its circumference and an arrangement of thin sheets provided between the plate cylinder and the printing plate.
2. Description of the Prior Art
Conventionally, a support sheet composed, for example, of oiled paper, is arranged between the plate cylinder and the printing plate. However, this prior art arrangement is still distinguished by a very large amount of friction between the actual plate cylinder and the printing plate caused, in particular, by the rough surface of the plate cylinder resting on the relatively rough surface of the oiled paper and also the rough underside of the printing plate resting on the upper face of the support sheet which has the same roughness as its underside. For explanation, it should be mentioned that when a printing plate is tightened by way of a tensioning strip at an end-of-printing location, a force arrives at the start-of-printing location which is only about one fifth of the force at the end-of-printing location of the printing plate. The remainder of the force is lost due to friction. After retightening by way of the tensioning strip at the start-of-printing location, the force at the tensioning strip at the start-of-printing location is approximately equal to 0.6 times the force at the end-of-printing location. Here again, the remainder, that is, about 40% of the force, is lost due to friction.
However, this high coefficient of friction between the plate cylinder and the printing plate is a drawback, particularly if the printing plate is to be retightened on the plate cylinder or is to be otherwise aligned to come into registration. In this connection it must also be considered that only limited forces should act on the printing plate in order not to unduly deform it.